This invention concerns a method for preparing non-agglomerating mixed bed ion exchange resin systems without affecting the ion exchange kinetics of the anion exchange resin component of the mixed bed system. More particularly it concerns a method for neutralizing the surface charges of the anion exchanging component of the mixed bed system by treatment with a sulfonated poly(vinylaromatic) polyelectrolyte.
The use of mixed bed ion exchange resins for deionization of aqueous solutions is widespread. Surface interactions between the cationic and anionic resin particles cause clumps or agglomerates of resin to form that lead to poor flow distribution in the bed and hence inefficient operation. Various approaches used to overcome this undesirable agglomeration include treatment with water-insoluble crosslinked ion exchange emulsion particles (U.S. Pat. No. 4,347,328), and treatment with water-soluble resinous polyelectrolytes to neutralize the surface charges of the treated resins (U.S. Pat. No. 2,961,417). Treatment with insoluble ion exchange emulsion particles (U.S. Pat. No. 4,347,328) involves high usage levels and extensive washing of the treated resin to remove the emulsion particles; and treatment with water-soluble resinous polyelectrolytes (U.S. Pat. No. 2,961,417) reduces mixed bed agglomeration but also reduces the ion exchange kinetics of the treated resin, thereby lowering the overall efficiency of the mixed bed system.
Despite the aforementioned attempts to produce non-agglomerating mixed bed ion exchange systems, no previous treatment has been found to be completely effective at low use levels for declumping mixed bed systems efficiently while having negligible effect on the performance (such as ion exchange kinetics) of the treated resins to produce purified water. No one had, heretofore, discovered that if certain water-soluble polyelectrolytes of selected molecular weights were used at specific treatment levels, that the best combination of non-agglomeration and mixed bed ion exchange kinetics could be achieved.
The present invention seeks to overcome the problems of the prior art by providing an improved process for preparing non-agglomerating mixed bed ion exchange systems without significantly affecting the ion exchange kinetics.